Humans Perceive Binocular Rivalry and Fusion in a Tristable Dynamic State

Abstract

Human vision combines inputs from the two eyes into one percept. Small differences "fuse" together, whereas larger differences are seen "rivalrously" from one eye at a time. These outcomes are typically treated as mutually exclusive processes, with paradigms targeting one or the other and fusion being unreported in most rivalry studies. Is fusion truly a default, stable state that only breaks into rivalry for non-fusible stimuli? Or are monocular and fused percepts three sub-states of one dynamical system? To determine whether fusion and rivalry are separate processes, we measured human perception of Gabor patches with a range of interocular orientation disparities. Observers (10 female, 5 male) reported rivalrous, fused, and uncertain percepts over time. We found a dynamic "tristable" zone spanning from ϳ25-35°of orientation disparity where fused, left-eye-, or right-eye-dominant percepts could all occur. The temporal characteristics of fusion and non-fusion periods during tristability matched other bistable processes. We tested statistical models with fusion as a higher-level bistable process alternating with rivalry against our findings. None of these fit our data, but a simple bistable model extended to have three states reproduced many of our observations. We conclude that rivalry and fusion are multistable substates capable of direct competition, rather than separate bistable processes.

Adaptation to transients disrupts spatial coherence in binocular rivalry

“…While often overshadowed by discussions surrounding consciousness, BR also reflects how the eyes interact and strive for a stable, coherent percept. It is therefore necessary to understand under which circumstances dichoptic images fuse versus when they engage in binocular rivalry (e.g., [15][16][17][18] . Especially now, with the rise of virtual and augmented reality goggles, it is of importance to understand how images can be best designed to prevent BR, enhance the fusion of representations of both eyes, and create realistic depth perception.…”

Binocular fusion enhances the efficiency of spot-the-difference gameplay

“…are not as strong a stimulus for binocular rivalry as orthogonal stimuli (e.g. orthogonally-oriented Gabor patches typically used to elicit binocular rivalry) is supported by a recent study by Risen et al who showed distinct epochs of fusion and rivalry for the former-type of stimuli than the latter [22]. Perhaps, the shape differences in the present study sometimes elicited an experience of fusion in our participants during the scan sequence, thus making its identification difficult compared to polarity differences.…”

Spatially distributed computation in cortical circuits

“…Neural waves in two spatial dimensions. The model of wave interaction in neural circuits is readily generalizable to two spatial dimensions, suited to study cortical selectivity for stimulus orientation (40,41), shape (33,35,42,43), and stereoscopic depth (44,45). It is equally suited to study temporal interactions between successive stimuli (34,46,47) and the interaction between spatial and temporal dynamics of cortical activity (48,49), in cortical area MT and other cortical areas.…”